The present invention relates to a composition that contains a cross-linkable matrix precursor and a poragen, and a porous matrix prepared therefrom.
As semiconductor devices become smaller and smaller, and chip packing densities increase correspondingly, undesirable capacitatance related delays and cross-talk between metal interconnects are more acutely manifested. Since capacitance related delays and cross-talk relate to the dielectric constant of the insulator, attention has focused on the creation of ultra-low dielectric constant materials (that is, dielectric materials having dielectric constants of ≧2.0). Such efforts include creating porous inorganic (for example, silicon dioxide) or thermoplastic polymeric (for example, polyimide) materials.
Silicon dioxide, which has been the dominant inter-level dielectric material (ILD) for the past 40 years, can be made porous by well-developed sol-gel techniques such as those disclosed in Proc. Mat. Res. Soc. 381, 261 (1995); Proc. Mat. Res. Soc. 443, 91 (1997); and Proc. Mat. Res. Soc. 443, 99 (1997), which teachings are incorporated herein by reference. Although the introduction of pores into silicon dioxide causes a reduction of dielectric constant from 4.2 to less than 2.0, the resultant porous material is significantly weakened. Thus, porous silicon dioxide is impractical as a low dielectric constant material.
Porous thermoplastic polymers, particularly thermally stable polymers such as polyimides, have also been investigated for use as ultra-low dielectric materials. See, for example, U.S. Pat. Nos. 5,895,263 and 5,776,990. Although these porous thermoplastic materials can be made to have acceptable dielectric constants, the pores tend to collapse during subsequent high temperature processing, thereby precluding the use of these materials for the applications of interest.
In view of the deficiencies in the art, it would be desirable to have an ultra-low dielectric material that is stable to the severe processing conditions required in fabricating semiconductors.